|l!!l!!lllllllll1llllllli:illll!ll!lllll(!IIJi;illll!lllillllllllllllil|{|||||||||||||||||||lh^ 

I THE PRESERVATION I 



= OF ^ 

I Iron Structures | 

j FROM RUST. j 

I NATURE AND COMPOSITION OF BAR AND CAST | 

I IRON, AND THEIR BEHAVIOR UNDER THE | 

I INFLUENCE OF THE ATMOSPHERE, j 

i MOISTURE, ACIDS, ETC. I 



-7 

Copyrighted 1890. 



BROOKLYN : 

Press of Brooklyn Eagle Book Printing Dei 't. 



■M 1890. : 

^f[|||l1lllllllllllllllll]||||lilllllll!llll!lillllllllllllllllllllil!lllllll!lllllllllll!lllllllll^ 



THE PRESERVATION 



OF 



Iron Structures 






M 



FROM RUST. 

NATURE AND COMPOSITION OF BAR AND CAST 

IRON, AND THEIR BEHAVIOR UNDER THE 

INFLUENCE OF THE ATMOSPHERE, 

MOISTURE, ACIDS, ETC. 



? n 



Copyrighted i8go. 




BROOKLYN : 

Press of Brooklyn Eagle Book Printing Dep't. 






TOL^O 




l-Hl^c-i 



BAR IRON. 

Good bar iron contains as its important constitu- 
ent from i to i per cent, of carbon. It also usually 
contains more or less Sulphur, Phosphorus, Silicon 
and Manganese, the two former exerting a deleteri- 
ous effect, silicon less so, while manganese is not 
only not harmful, but in many cases beneficial. 

The color of bar iron is light gray, sometimes blu- 
ish gray, almost silver white, sometimes dark gray ; 
varying with the amount of the above mentioned 
materials it contains. Its specific gravity varies from 
7-3 to 7.9. It expands ttAuo" of its length for one 
degree of heat. Compared with cast iron, its strength 
is 1. 1 2 times, its extensibility 0.86 times, and its stiff- 
ness 1.3 times. 

A piece of bright bar iron can be kept in perfectly 
dry air, or in water free from air, for a long time, 
before it begins to lose any of its polish by oxidation; 
but just as soon as moisture and air combined have 
a chance to act on it, oxidation sets in and the iron 
rusts, which increases more rapidly the more carbonic 
acid is present. This latter, when no other acid is 
present, is undoubtedly the chief cause of the rusting 
of iron, although iron may be kept in a dry atmos- 
phere of carbonic acid without showing any signs of 
rust whatever. According to Marshall Hall, iron in 
water saturated with carbonic acid rusts very rapidly, 
with a visible evolution of hydrogen gas. Not only do 
electronegative and distinctly acid substances, like car- 



bonic acid, cause iron to rust, but likewise fully neu- 
tral salts accelerate the action when dissolved in 
water in which iron is immersed, or when strewn over 
the surface of iron in a damp atmosphere. In this 
case the iron rust seems to consist of a very basic 
oxide, containing a slight portion of the acid of the 
dissolved salt. If in place of a neutral salt an alka- 
line salt be dissolved in water, such as caustic potash 
or caustic lime, and polished iron be put into the 
solution, the rusting is entirely suspended. 

CAST IRON. 

The chemical difference between bar and cast iron 
consists principally in the fact that the latter contains 
a much larger percentage of carbon. It also contains 
more impurities, Silicon, Sulphur, Phosphorus, Arse- 
nic, Zinc, Manganese, Titanium, Chromium, Alumin- 
ium, Magnesium and others. There are two varieties 
of cast iron, the white and the gray. In the white 
variety all the contained carbon is chemically com- 
bined with the iron; in the gray variety, on the other 
hand, only a portion of the carbon is chemically com- 
bined, while the rest exists in the form of admixed 
graphite. The color of cast iron varies from silver 
white, containing the largest amount of combined 
carbon, to a dark, almost black, gray. 

Cast iron expands ye'sWo" o^ its length for one 
degree of heat ; exposed to direct sun ray it expands 
ToVo ^^^ shrinks in cooling -^^ of its length. 

Cast iron under the same circumstances as 
those described under bar iron, oxidizes less readily 
than gray iron, and this again less readily than bar iron, 



provided that it does not contain a large amount of 
sulphur, and is not very much contaminated with easily 
oxidizable substances. 

THE USE OF OIL COLOR (PAINT). 

The greater portion of so-called compositions, 
consisting generally of solutions of resins or tar pro- 
ducts for protecting iron from rusting, are not only 
valueless, but even in not a few instances absolutely 
deleterious. Up to the present time no substance has 
been found which, under varying atmospheric influ- 
ences, and especially under great changes in tempera- 
ture, will adhere so firmly to iron as a good drying oil 
paint. Even in those cases (comparatively rare) 
where a coating with some other metal, less liable to 
oxidation, is found useful, oil color is still the last 
resort, when in the course of time the metallic coat- 
ing disappears or is worn off. But the painting of 
iron as done heretofore is far from satisfactory, espe- 
cially where this material is used in ship-house or 
bridge building, it is found that ordinary oil paint does 
not properly protect it against the disturbing action 
of the atmosphere, owing to the fact that in a compar- 
atively short time the paint or composition becomes 
cracked or broken, and though these crevices may be 
microscopical, they are sufficient to allow air and mois- 
ture to penetrate to the iron, and the work of destruc- 
tion thus begun continues, in many cases, unsuspect- 
ed, till eventually the whole structure is honeycombed 
and rendered useless. So that it is all important to 
have a material for the protection of iron which will 
last a reasonable length of time. 



IMPORTANCE OF THE PRIMING COAT. 

In painting iron, the vital point is the first, or so- 
called priming coat ; if this is not properly applied 
the result is a failure, even though the later or finish- 
ing coats are put on in the most skillful manner, for 
though these may adhere to one another, yet if the 
underlayer or priming does not adhere to the iron 
itself, the whole will gradually crack and chip off, 
scale. 

RED-LEAD AND METALLIC OXIDES. 

Formerly Red-lead was exclusively used as a priming 
coat. For the last few years the so-called "metallics" 
(oxides of iron) have come into use for painting iron. 
It has been much disputed which was the better for 
this purpose, and it has been frequently asserted, 
though no confirmatory evidence has been offered, 
that Red-lead, by its decomposition, causes the 
destruction of the oil coating. I am convinced that 
there is no substantial foundation for this belief, 
for thorough tests and examinations of old iron coat- 
ings, extending over several years, have failed to 
reveal any decomposition of the Red-lead. Metallic 
oxides do frequently exert a deleterious influence, if 
not carefully prepared. ]\Iany of them being made 
by burning iron vitriol (sulphate of iron or copperas) are 
not thoroughly washed, and consequently retain a 
greater or less amount of sulphuric acid. A simple 
test will show the presence of sulphuric acid. If an 
oil color, wash with benzine, to remove the oil, treat 
the dry powder with hot water, settle and filter, add a 



few drops of muriatic acid, and then add solution of 
chloride of barium. A white precipitate indicates the 
presence of sulphuric acid or a salt thereof. 

THE VEHICLE OR VARNISH. 

It must be evident to anyone who has made a care- 
ful study of this matter that the trouble is with the 
vehicle, and that to prepare a priming coat which 
shall be lasting and serve to preserve the iron, the 
varnish must itself be of the right character. 

PREREQUISITES OF THE PRIMING COAT. 

Now what are the prerequisites of a priming coat on 
iron to render it adherent and lasting? First, it must 
dry well, viz : It must form an unbroken elastic coat- 
ing, not necessarily hard, rather otherwise, as being 
less liable to crack or break under expansion. Second, 
it must not be too thick. Third, it must be applied in 
a thin layer. Fourth, the surface of the iron must be 
clean and free from rust or old paint. Good drying 
(or setting) in order that no moisture may be 
deposited on the iron, when the air becomes cooler ; 
this occurs generally after sundown. In such case the 
moisture forms an emulsion with the varnish, and as a 
consequence the varnish never dries evenly ; hence, 
when practicable the work should be gone over during 
the morning hours and in dry weather. Moisture may 
likewise be deposited by radiation of heat from the 
iron. The radiation of iron like that most other metals 
is comparatively slight, but Mellom's investigations 



8 



have shown that it is very perceptibly increased when 
the metalUc surface is coated with varnish. 

The priming coat should be sufficiently thin to 
insure perfect contact with the minutest inequalities 
of the surface ; if this is neglected, which is usually 
the case when the varnish is too thick, and the painter 
does not give the requisite attention to this point, the 
coating tears or breaks easily when the metal expands, 
air and moisture enter through the crevices thus 
formed, and the consequent rusting of the iron soon 
undermines the whole coating. 

The coating should be applied in a thin layer, as a 
layer of varnish on iron or any other non-porous sub- 
stance dries but slowly. If the coating is thick, only 
the outer surface dries, forming a thin skin, leaving 
the under parts fluid for a long time. The surface of 
the iron should be clean and free from rust, and in 
most cases this can be accomplished by scrubbing and 
brushing the surface well with ordinary kerosene, 
which removes any grease, loosens the scale, and 
assists in carrying the varnish into the minute cavities 
of the metal. To a certain extent it retards the drying 
of the varnish, but this is more than compensated for 
in the end by its beneficial action. 

QUICK DRYING \^ARMSHES. 

In order to produce a priming coat, having the 
above described qualities, it seems self-evident that the 
varnish or medium is the all-important thing, but hereto- 
fore no varnish has been produced possessing just these 
qualities. Quick drying varnishes may be produced 
in two wavs: either the varnish is boiled till it becomes 



thick, or so-caUed dryers may be added to it. But a 
thick varnish is unsuitable for reasons given above, 
viz: that it does not come into intimate contact with 
the whole surface of the iron. The only liquid dryer 
of any value is nothing more or less than a thick boiled 
oil, thinned with turpentine, but for the following rea- 
sons this cannot be advantageously used. 

BENZINE AND TURPENTINE. 

Neither benzine nor turpentine are suitable for thin- 
ing varnish to be applied to iron. By their rapid 
evaporation they cool the iron and thus cause a precipi- 
tation of moisture, producing an emulsification of the 
varnish, as above mentioned ; which shows itself by 
the varnish becoming cloudy. Furthermore, turpen- 
tine always contains more or less organic acid, ambic, 
formic, acetic, which is increased, by exposure to the 
air and consequent oxidation, and this in time reacts 
on the iron. 

TIEMANN'S IRON PRESERVATIVE. 

After much study and experimenting, and profiting 
by the experience of others who have given careful 
attention to this matter, I have produced a varnish, 
which, while possessing the requisite fluidity, dries well, 
though never becoming absolutely hard, forming an 
India rubber-like coating on the surface of the iron, 
expanding and contracting with the metal, and form- 
ing a coating impervious to air and moisture. 

J. H. TIEMANN. 
Brooklyn, N. Y., April 15, 1890. 



lO 



TIEMANN'S IRON PRESERVATIVE. 

For the preservation of all structural iron work, 
house, ship, railroad and bridge buildings, tin roofs, 
smoke stacks, boilers, iron railings, etc. 

A perfect preservative against the action of the 
atmosphere, moisture or changes in temperature. 

J. H. TIEMANN, 

Sole Manufacturer, 
SS Fulton Street, Brooklyn, N. Y. 



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